Amplifiers are commonly used in various electronic devices to provide signal amplification. Different types of amplifiers are available for different uses. For example, a wireless communication device such as a cellular phone may include a transmitter and a receiver for bi-directional communication. The transmitter may include a driver amplifier (DA) and a power amplifier (PA). The receiver may include a low noise amplifier (LNA), and the transmitter and receiver may include variable gain amplifiers (VGAs).
A transmitter may have an amplifier module that may include multiple amplifiers (e.g., a driver amplifier and a power amplifier). In some wireless transmitters of the wireless communication device, a driver amplifier has a differential-to-single-ended transformer (e.g., a balun) as its load and can provide single-ended outputs. Some power amplifiers are differential power amplifiers and therefore specify a single-ended-to-differential balun at their input when driven in accordance with a single-ended input. The design of such transformer load circuits of the amplifiers involves balancing various tradeoffs.